ASTM D2448-85(2002)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D 2448 – 85 (Reapproved 2002)
Standard Test Method for
Water-Soluble Salts in Pigments by Measuring the Specific
Resistance of the Leachate of the Pigment
This standard is issued under the fixed designation D 2448; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope measurements, however, cannot be used as the only method to
determine and compare the amount of water soluble salts of
1.1 Thistestmethodcoversthedeterminationofthespecific
pigments with the same chemical composition but produced by
resistance of the aqueous leachate from a pigment as an index
different manufacturing processes.
of water-soluble salt content. This test method is applicable to
white pigments and colored pigments (organic and inorganic).
5. Apparatus
The water-soluble salts content is a function of the specific
5.1 Centrifuge (optional), having a 500-mL capacity per
resistance of the solution formed by extracting the pigment
cup.
with water.
5.2 Filter Paper (Note 1)—For high reliability avoid use of
1.2 This test method is based on a water to pigment ratio of
filter paper containing soluble material. Each filter should be
9+1. The leachate yield (minimum 160 mL) sufficient for
washed with reagent water in the funnel until resistance of the
rinsing the cylinder dip cell and thermometer plus the mini-
filtrate is greater than 200 000 V · cm.
mum 80 mL required for the measurement to determine the
quantity of pigment to be used.
NOTE 1—The size of the filter paper will be determined by how
1.3 This standard does not purport to address all of the voluminous the pigment is. Some organic pigments require at least a
185-mm paper for proper filtering.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
5.3 Filter Aid (optional)—The use of a filter aid may be
priate safety and health practices and determine the applica-
desirable with some pigments to improve filtration. However,
bility of regulatory limitations prior to use.
the filter aid must be treated to meet the same specifications for
filter paper as given in 5.2.
2. Referenced Documents
5.4 Ungraduated Cylinders, approximately 35 mm wide by
2.1 ASTM Standards:
125 mm deep.
D 1193 Specification for Reagent Water
5.5 Thermometer, graduated in 0.2°C intervals.
5.6 Conductivity Bridge.
3. Summary of Test Method
5.7 Conductivity Cell, having a cell constant, K,of1.The
3.1 A weighed quantity of pigment is added to water and
cell constant recommended for various ranges of electrolytes is
boiled. For hydrophobic pigments methyl alcohol is used to
as follows:
facilitate wetting. After filtration, the specific resistance of the
5.7.1 For specific resistances of less than 250 V· cm, use a
filtrate is determined using a conductivity bridge.
cell with a constant of 10 or more.
5.7.2 For specific resistances from 250 to 200 000 V· cm,
4. Significance and Use
use a cell with a constant of 1. This covers the range for most
4.1 This test method provides a reliable means for the
pigments.
determination of the relative amounts of these salts when
5.7.3 For specific resistances of reagent water or of over
comparing different lots of the same pigment grade. Water-
200 000 V · cm, use a cell with a constant of 0.1.
soluble salts also affect the water resistance and blister resis-
tance of coatings, especially primers for steel. Conductivity 6. Reagents
6.1 Purity of Reagents—Reagent grade chemicals shall be
used in all tests. Unless otherwise indicated, it is intended that
This test method is under the jurisdiction of ASTM Committee D01 on Paint
and Related Coatings, Materials, andApplications and is the direct responsibility of
Subcommittee D01.31 on Pigment Specifications.
Current edition approved Nov. 29, 1985. Published January 1986. Originally
e1 3
published as D 2448 – 66 T. Last previous edition D 2448 – 73 (1979) . Any commercially produced conductivity bridge and conductivity cell is
Annual Book of ASTM Standards, Vol 11.01. satisfactory.
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D 2448
TABLE 1 Specific Resistances of Solutions of Potassium
all reagents shall conform to the specifications of the Commit-
Chloride at 25°C
tee onAnalytical Reagents of theAmerican Chemical Society,
Normality V·cm
where such specifications are available. Other grades may be
0.001 6802 (1)
used, provided it is first ascertained that the reagent is of
0.002 3427 (1)
sufficiently high purity to permit its use without lessening the
0.005 1393 (1)
accuracy of the determination.
0.01 707.3 (1,2)
6.2 Purity of Water—Unless otherwise indicated, references 0.02 361.5 (3)
to water shall be understood to mean reagent grade water as
defined by Type II of Specification D 1193.
6.3 Methanol.
can be handled better in a larger beaker. Usually 20-g speci-
6.4 Potassium Chloride, Standard Solution (0.02 N)— Pre-
mens of organic pigments require a 600-mL beaker to allow
pare a 0.02 N potassium chloride (KCl) solution with water by
adequate room for foaming. Boil slowly for 5 min with
dissolving 1.491 g of KCl (heated before weighing for1hat
occasional stirring. Cool to about 60°C and add water to bring
105°C) in water, followed by dilution to 1 L.
the net weight back to 200 g. Stir thoroughly. Filter directly
through fine-texture paper (Note 1) or separate the solids by
7. Determination of Cell Constant
centrifuge using clean, dry cups, or cups wa
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